A mantra is a means of concentrating and directing a specific quality of the Supreme Self for a purpose. A mantra need only be said once, but is only effective if uttered in a true state of meditation: a state in which the utterer is one with the Self. The formula of a real mantra will always acknowledge that the divinity or quality being invoked is truly a part of the Single Supreme Self. Mantras are composed in Sanskrit, an ancient Indo-European language with marked similarities to Latin and Greek. A form of Sanskrit called Pali spread, with Buddhism, as far East as Japan. A true mantra, in the ancient Sanskrit language, begins by addressing the Supreme Self thus: om twameva sakshat..., which means something like "Amen, verily Thou art...", then names a deity or archetypal principle. Mantra is an important feature of religions which originate in India, such as Hinduism, Buddhism, Jainism and Sikhism. The Zoroastrian religion of ancient Iran also has the practice of mantra (called manthra in the Avestan language, a close relative of Sanskrit).
"The Sanskrit word mantra- (m. मन्त्रः, also n. मन्त्रं) consists of the root man- "to think" (also in manas "mind") and the suffix -tra meaning, 'tool', hence a literal translation would be "instrument of thought".
Another explanation is that the suffix -tra means "protection".
The Chinese translation is zhenyan 眞言, 真言, literally "true words", the Japanese on'yomi reading of the Chinese being shingon."
The famous Gayatri Mantra invokes "the universal Brahman as the principle of knowledge and the illumination of the primordial Sun" -Wikipedia :
Om Bhūr Bhuva Svaha
Tat Savitur Varenyam
Bhargo Devasya Dhīmahi
Dhiyo Yo Nah Prachodayāt.
The Supreme Self, coextensive with the Universe, is available at all times and places, but as the self-realised writer Franz Kafka realised, it is sometimes necessary to invoke it in one of its infinite variety of aspects.
but veiled from view,